Reshaping and relaxing human hair constitutes a substantial portion of the cosmetic/ beautician industry. Huge sums of money are spent on compositions and services in salons and in the home.
Hair is a proteinaceous material composed of .alpha.-keratin which includes in various amounts, sulfur bonds which contribute to the macroscopic shape of a strand. Reshaping or "perming" hair generally involves breaking the naturally occurring bonds and reforming the bonds to achieve a desired result. This may be accomplished by heat to a certain extent, but for long-term shape retention chemical treatment is preferred.
In the context of conventional materials used for the reshaping of hair commonly referred to as giving "a permanent", here are two broad classes. The first includes malodorous thio-alcohol/acid derivatives such as thioglycolic acid, thiopropionic acid, monothio-glycerol, etc Treatment includes a rinse step with an appropriate oxidizer in a carefully controlled application.
The second general treatment involves the use of relatively strong caustic alkaline solutions formed from hydroxides of alkali and alkaline earth elements such as sodium hydroxide, calcium hydroxide, etc. With such treatment, it is necessary to further treat the hair with a neutralizing wash to obtain a physiologically compatible pH. It is known in the cosmetic industry that both of the above-specified treatments are harsh and may adversely affect the scalp or, if employed improperly, the hair itself. For example, the "neutralizing" step requires careful application in order to prevent exposure of the hair to too much or too little of the appropriate reagents.